1. Field of the Invention
The invention relates generally to a computer controlled imaging system and, more particularly, to a digital image processing system which has the ability to compose and construct a sequential stream of scenes for a display from a library of images with sufficient processing speed to permit real-time or near real time analysis of the images by a human operator or a hardware/software equivalent thereof.
One example of the many possible applications of such a system relates to the field of vehicle simulation such as aircraft flight simulation. In such a system a visual subsystem within the aircraft flight simulation system receives flight data from a flight simulation computer and terrain data from a defined or "gaming area" data base. A data processing system within the visual simulation system organizes the flight data and terrain data to produce a simulated visual display as it would appear to an observer in the cockpit of the aircraft.
The visual system of a vehicle simulator which may be, for example, a helicopter simulator, involves a "window view of the simulated surroundings" and controls for guiding the "vehicle" in any desired direction relative to such surroundings. The term "window view" of the system herein is a display, normally in video form, of a simulated environment which corresponds to a terrain covering a large area which may be on the order of 25 to 100 square miles, for example. The simulated environment is referred to herein as a defined area or gaming area.
The operation of the controls of the vehicle guides the vehicle in, around and through the gaming area and it is the system response to the vehicle controls which determines what is seen in the window, that is, the video display. What is seen in the "window" is referred to as the field of view or FOV.
2. Description of the Prior Art
One system in the prior art known as "Computer Generated Imagery" (CGI) system utilizes a computer system to generate video displayable imagery from a data base. In the CGI system objects and surfaces for constructing video displayable scenes are derived from purely mathematical models stored in the form of points which define the limits of the objects and surfaces.
The strength of CGI is in its surface representation. A real or artificial surface can be measured to get elevations at specified points, usually at intersections of a uniform grid. The surface can be reconstructed in a computer by connecting sample elevations. In addition to realistic surface representation, CGI offers control over the placement of objects on the surface. Since the data of elevations is usually provided with a uniform grid, the placement of other objects can be specified on this same grid. Typical objects such as trees, rocks, shrubs, houses and roads can all have their positions defined in the data base grid system.
Correct illumination and perspective are also major contributions from CGI. Correct illumination is achieved by finding the surface normal for each pixel displayed. This normal is used along with line-of-sight and the normal from the illumination source, plus an ambient intensity and haze factors, to compute an intensity for a pixel. Correct perspective is achieved because the distance from the observation point to each surface point is known. This distance is a significant variable in the perspective transformation.
A weakness of CGI is lack of realism. Although an object can be accurately positioned, correctly illuminated and displayed in correct perspective, the object itself cannot be realistically presented. The current state of the art in CGI object presentation is such that objects appear overly cartoonish. Some scene elements, such as barren terrain, sand and clouds can be represented more realistically than highly structured objects like trees and grass or detailed man-made objects. Such detailed objects simply lack realism.
Another imaging system is conveniently referred to as "Computer Synthesized Imagery" or CSI. The CSI technology also generates images such as, for example video displayable images, from a data base but the objects and surfaces stored in its data base are represented as real-world electromagnetic media images of objects and surfaces rather than mathematical models thereof as in CGI.
Thus, whereas CGI uses a computer to generate imagery from a purely mathematical data base, CSI uses a computer to insert objects into a scene based on stored real-world images. Although CGI provides excellent control of a scene to be constructed and displayed for interaction in an environment, the fidelity is low and thus realism in the displayed scene is poor. CSI is just the opposite. Whereas fidelity is excellent, the control over scene construction is restricted.
The strength of CSI lies in its use of real images such as photographs in the scenes. With currently available video equipment the photographic data can be readily manipulated. Literally thousands of individual photographs can be stored on video disks, and access to them may be controlled by an indexing system just as is the case with digital data stored on magnetic disks. Moreover, the fidelity of the image is true and the outputted image is precisely the same as the inputted, stored image.
A weakness of CSI is that its scenes are limited to the view point of the "camera". That is, one cannot dynamically navigate a scene unless a series of through-the-scene photographs is used. For any reasonable size gaming area, the number of through-the-scene photographs may be prohibitive.